Interaction between the homeodomain proteins Cdx2 and HNF1α mediates expression of the lactase-phlorizin hydrolase gene

Abstract

Lactase-phlorizin hydrolase is a brush-border enzyme which is specifically expressed in the small intestine where it hydrolyses lactose, the main carbohydrate found in milk. We have previously demonstrated in transgenic mice that the tissue-specific and developmental expression of lactase is controlled by a 1 kb upstream region of the pig lactase gene. Two homeodomain transcription factors, caudal-related homeodomain protein (Cdx2) and hepatic nuclear factor 1alpha (HNF1alpha), are known to bind to regulatory cis elements in the promoters for several intestine-specific genes, including lactase, and are present in mammalian intestinal epithelia from an early stage in development. In the present study, we examined whether Cdx2 and HNF1alpha physically interact and co-operatively activate transcription from the lactase-phlorizin hydrolase promoter. We show that the presence of both factors leads to a much higher level of transcription than the sum of the activation by either factor alone. The N-terminal activation domain of Cdx2 is required for maximal synergy with HNF1alpha. With the use of pull-down assays, we demonstrate a direct protein-protein interaction between Cdx2 and HNF1alpha. The interaction domain includes the homeodomain region of both proteins. This is the first demonstration of a functional interaction between two transcription factors involved in the activation of a number of intestine-specific genes. Synergistic interaction between tissue-restricted factors is likely to be an important mechanism for reinforcing developmental and tissue-specific gene expression within the intestine.

CDX2 homeoprotein is involved in the regulation of ST6GalNAc-I gene in intestinal metaplasia

“…Dynamic cooperation between CDX2 and other partners is not a rare phenomenon and has been demonstrated for other genes. [35][36][37] The regulation of glycosyltransferases by CDX2 has been described, 24,27 in particular the transcriptional control of β3Gal-T5 in the Caco-2 intestinal cell line. 24 This cellular model expresses increasing amounts of CDX2 20 and also alters its glycosylation profile and enzyme expression/activity along enterocytic differentiation, [21][22][23][24][25][26] suggesting that CDX2 can act as a regulator of the glycosylation in this cell line.…”

Physical Interaction between GATA-5 and Hepatocyte Nuclear Factor-1α Results in Synergistic Activation of the Human Lactase-Phlorizin Hydrolase Promoter

“…We therefore hypothesize that coexpression of GATA factors and HNF-1␣ is necessary, but not sufficient, for high levels of cellspecific LPH gene expression. Interaction with other tissuerestricted transcription factors and cofactors such as SP-1 (44), FOG-2 (62, 63), Cdx-2 (20), and the dimerization cofactor of HNF-1␣ (64) as well as other information farther upstream in the LPH promoter (18,65) must be considered when characterizing specific expression of the LPH gene in vivo.…”

“…Identification of specific binding sites within the first 100 bp of 5Ј-flanking region in the LPH genes of several species has led to the demonstration that GATA, hepatocyte nuclear factor-1␣ (HNF-1␣), and Cdx-2 transcription factors are activators of the LPH promoter (15)(16)(17)(18)(19)(20)(21). Due to the close proximity of GATA and HNF-1 binding sites on the LPH promoter and the nearly exclusive coexpression of these two families of transcription factors in the intestinal epithelium (22)(23)(24)(25)(26)(27)(28)(29), we hypothesized that members of the GATA and HNF-1 families of transcription factors interact to modulate LPH gene expression.…”

Hepatocyte nuclear factor-4α promotes differentiation of intestinal epithelial cells in a coculture system

“…HNF-1␣ was shown to participate in the transcriptional regulation of several intestinal specific genes (6,11,31,46,57,60). HNF-4␣ was recently suggested to act as a regulator of villus specific epithelial genes (53).…”

“…Cdx2, an intestinal epithelial specific transcription factor, regulates transcriptional activity of several intestinal epithelial-specific genes [for a review, see Guo et al (17)]. Other transcriptional regulators such as GATA-4 or hepatocyte nuclear factor-1␣ (HNF-1␣) cooperate with Cdx2 and regulate transcription of sucrase-isomaltase (SI) (6), lactase-phlorizin hydrolase (31,56), calbindin 3 (60), liver fatty acid binding protein gene (52), and claudin 2 (13,46). Restriction of apolipoprotein A-IV (ApoA-IV) expression to villus-differentiated enterocytes has been functionally linked to hepatocyte nuclear factor-4␣ (HNF-4␣) (49).…”